
9.21
Silberschatz, Galvin and Gagne ©2005
Operating System Concepts – 7
th
Edition, Feb 22, 2005
Thrashing
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If the number of frames allocated to a low priority process falls
below the minimum number required by the computer
architecture , If a process does not have “enough” pages in
memory, it will quickly page fault at this point it must replace
some page. Since all the pages are active in use, it must replace
a page that will be needed again right away. Consequently, it
page faults again, and again and again…. the page-fault rate can
be very high. This leads to:
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Low CPU utilization and low throughput
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OS attempts to increase the degree of multiprogramming
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Another process added to the system
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Even more page faults ensue.
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Thrashing
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a process is busy swapping pages in and out
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This high paging activity is called thrashing.